EFFECTS OF DROUGHT ON SOME ECOPHYSIOLOGICAL TRAITS OF SESSILE OAK (Quercus petraea L.)

Responses of some physiological traits of Quercus petraea to drought was studied at the Sikfokut research site in the dry and humid growing seasons of 2003 and 2004. Drought reduced significantly the leaf mass increment of Quercus petraea in the dry year (2003). SLM was lower in 2003 than in 2004. Chlorophyll content showed inter-annual and within-canopy variability. As indicated by the low values of the Fv/Fm chlorophyll fluorescence parameter the photosynthetic apparatus exhibited high susceptibility to abiotic stress factors in early spring. Carotenoid content and VAZ cycle pool per chlorophyll basis was 1,5-2 times larger in spring than in summer. In summer of 2003 VAZ pool was larger especially in sun leaves than in 2004. Values of Fv/Fm were lower in 2004 than 2003 which indicated lasting drought effects on the photochemical activity of leaves of sessile oak.